Re: CHEVROLET BY THE NUMBERS 1960-1964, page 220
Hello Alan,
 My name is Dave Heitzman, I am the current NCRS 61-62 team leader.  We are currently in the process of writing the next edition of the NCRS 61-62 Judging Guide and would appreciate your input.  Over the years questions have been submitted by our members regarding 4-speed transmission change to an aluminum main case.  Our manual currently states "early 1961 as late as VIN 2400 (approx 11/3/61) used the cast iron main case."  Information in your book indicates that use of the aluminum case started after 12/23/60. It would be of great help if you could answer the following questions.
[1] MAIN CASE CASTING NUMBER
     T10-1B until 1/61
     T10-1C after 1/61  
Does this indicate that cast iron case transmissions were installed until 1/61 and that aluminum case transmissions were installed after 1/61?  Is there any documentation available?
[2] "OCTOBER 1960 CHEVROLET SERVICE NEWS points out.."
Do you have a copy of this GM documentation?  Where could we get a copy?
[3] "The earliest recorded aluminum case T10 build date is 11/28/60."  How was this date recorded?  Is any documentation available?
[4] "The earliest documented aluminum case...12/23/60"
What kind of documentation does this refer to?  Can we get a copy of the documentation?
  For over 30 years NCRS has been writing and rewriting our manuals, adding information, providing greater detail and correcting errors.  When an NCRS manual is changed we must have documented information to support that change.  GM documentation is always best.  Other information obtained from several sources tends to agree with your book, but no one has any documentation and some of the sources said their information came from your book.  
  Any information that you can provide will be greatly appreciated.  
Regards,
Dave Heitzman  -  vettes6162@msn.com  

Dave,

Sorry for the delay. I haven't been checking my posts lately. Let me look into what I have and get back to you.

Alan Colvin